Scott Andrews of Cogenia Partners, LLC details the findings of the VII Proof Of Concept work carried out to verify the effectiveness of 5.9GHz-based communication for future US cooperative infrastructures
Reducing the number and severity of road transportation incidents is a top priority for the
To enable this vision, the US DOT formed a cooperative agreement with the Vehicle Infrastructure Integration Consortium (VIIC), a group of nine automakers including
The POC programme was used to evaluate the effectiveness of the overall architectural concept and to test the ability of DSRC to support a variety of safety, mobility and commercial applications.
VII Proof Of Concept overview
As part of the overall Vehicle Infrastructure Integration (VII) effort approximately 100 use cases were developed by various stakeholder groups. These use cases address key issues which stakeholders believed were relevant for the system. These included safety, mobility, management and commercial applications. Because developing and testing all of the use cases would have been impracticable, a subset was identified, implemented and tested to assess both the functionality and baseline performance of the system.
These requirements addressed the basic needs of the expected use cases, and formed the basis for the POC design, which supported: broadcast messages from network providers to vehicle OnBoard Equipment (OBE) at specified geographic locations; broadcast messages from Road-Side Equipment (RSE), such as traffic signals or toll stations, to OBEs in vehicles at specified geographic locations; broadcast messages between vehicles equipped with OBEs; data collection from vehicles, and distribution of topical information extracted from the data to subscribers; vehicle-borne OBEs' access to remote private service providers, which can be carried over from one roadside installation to the next; and security functions to protect against attacks and ensure the privacy of the individual users (Figure 1).
System architecture
OBEs send and receive messages between each other for
Vehicle-to-Vehicle (V2V) applications and also exchange messages with
RSEs. DSRC forms the link. The RSEs are connected to, and remotely
managed from, a Service Delivery Node (SDN). The SDN provides a variety
of services which are described below. An overview of the POC system
architecture is shown in Figure 1.
Each
RSE is connected to a regional SDN via a backhaul link, and each SDN is
connected to all other SDNs via a wideband backbone network. Using this
architecture, any RSE is accessible from any SDN. This is a key feature
of the system's scalability, since any user connecting to a local SDN
can interact with any RSE to obtain or send data to cars in the vicinity
of that RSE.
Each RSE is a
terminal node of the network. In the VII architecture, the RSEs are
intended to be located at roadway intersections and other strategic
points in the road network, to support delivery of important safety and
mobility-related messages, and to provide connection points for OBEs to
execute various data transactions.
The
primary functions of the SDN include: collection of probe data from
vehicles; distribution of probe data elements to network-based
subscribers; distribution of advisory messages provided by network users
to RSEs according to the geographic delivery instructions within the
message; collection and distribution of map-related information; and
routing of messages from vehicles to remote service providers.
The
POC development test environment included 55 RSEs placed at various
locations in the northwestern Detroit suburbs. These RSEs were linked to
the SDN using a variety of different backhaul technologies. The POC
implementation was a small-scale version of the national system
architecture, allowing the programme to test all aspects of operation
within a limited deployment.
The
OBE and a suite of applications were developed by a supply team led by
the VIIC. This unit included custom-developed DSRC radio and security
functions to conform to the DSRC standards. OBEs were installed in
vehicles and integrated with the vehicle systems, allowing applications
to obtain operational data directly from the vehicle CANbus.
POC
tests The objective of the POC was to assess the overall ability of the
system to perform the core functions described above. The POC tests
focused on three primary areas: Services Tests, which involved
quantitative assessments of specific functional elements of the OBE;
Application Tests, which used the OBE, and the vehicle operating in the
RSE network, to assess the overall system's ability to perform these
core functions; and Public Applications Tests, which exercised the
system at moderately large scales to observe system performance under
heavy use.
The tests included:
detailed characterisation of DSRC in multiple environments, ranging from
open roads to urban canyons and hilly terrain; accurate assessment of
OBE positioning capabilities; security subsystem performance tests;
probe data collection from vehicles and real-time distribution of the
data to subscribers; advisory message delivery to vehicles, based on
geographic location, and subsequent display of those messages under
specific geographic conditions; V2V messaging; Infrastructure-to-Vehicle
(V2I) safety messaging; open road toll charging and parking payments;
and request/response for services through a Web-based service provider.
POC programme results
The Service Tests showed that DSRC has substantially
better range than expected; in open road testing ranges of over 800m
were common. While impressive, this was also problematic, because DSRC
protocols were originally developed assuming that an OBE would interact
with a single RSE. When the OBE could hear multiple RSEs it had
difficulty choosing between them. In addition, since the RSE has a
higher transmitter power, the OBE could receive RSE messages beyond its
range of its response. In early testing, the OBE would hear the RSE and
send all of its probe data while out of range, resulting in substantial
data losses. These issues were resolved but it demonstrated the need for
slight revisions to the DSRC protocol. However, DSRC appears to be
highly effective for localised high-speed data communications with very
short connection times.
Geographic Advisories testing indicated that messages provided by an internet-based advisory service provider could be distributed quickly to the appropriate RSEs and delivered to passing vehicles with 99 per cent reliability. The advisories were then conditionally displayed to the vehicle occupants based on direction of travel and vehicle location. This is crucial, since the radio broadcasts of these messages effectively reach every vehicle in the RSE zone, despite their relevance being limited to cars in specific areas or travelling in specific directions. This refined geographic addressing of messages is a key feature of the POC architecture, and it worked flawlessly.
Probe data tests indicated that the system can collect a wide variety of data from vehicles. Tens of thousands of data snapshots were collected over the air, parsed into specific data topics, and distributed to subscribers. Figure 2 shows an example of position data for vehicles travelling in the area of a freeway interchange. As can be seen, these snapshots accurately depict the roadways that make-up the intersection. Similarly, data collected using factors such as windshield wiper status correlated accurately with weather maps derived from other sources.
Electronic tolling tests indicated that the system is effective. The POC included a freeway interchange with specific lanes and on-ramps designated as toll lanes. As the vehicle neared the interchange it received descriptions of the payment zones and when it passed through it would execute a payment transaction. The system was highly discriminatory, ignoring vehicles passing close by the payment zones (for example on a frontage road) and charging only those which were appropriate. The ability to provide precise lane charging, and to electronically change the details of rates and lanes, promises a new paradigm for time and location-based tolling and road charging.
Commercial services were demonstrated using a Web services-based off-board navigation application. Routes of various lengths were requested as the vehicle was passing through the RSE zone. Shorter routes (with fewer than 10 manoeuvres) were served during the initial RSE encounter. Longer routes were interrupted as the vehicle left the RSE zone and were then seamlessly resumed at the next RSE, allowing the vehicle to move from RSE to RSE while continuing long transactions when communications were available. Not only was this very effective, it means that the intermittent connectivity offered by DSRC does not appear to be a barrier to performing long transactions using conventional service architectures.
V2V and V2I communications were tested to determine their effectiveness. Generally, V2V communication was 99 per cent reliable up to about 50m, which represents 10 car lengths.
In conclusion, the POC programme results indicate that DSRC can be a viable communications technology for safety and mobility applications. The local nature of DSRC is particularly effective at efficiently delivering messages based on location. So, rather than sending messages to a particular network address, the POC system effectively allows a user to send a message to vehicles in a particular geographic area. This is an important differentiation over conventional communications systems that support one-to-one and wide area broadcast messaging but which could not scale to a nationwide system supporting hundreds of millions of car and millions of geographically unique messages.
The POC also demonstrated the viability of architectural concepts underlying the VII system, namely that it is feasible to deliver advisory messages to vehicles in particular locations, that it is possible to collect data from vehicles in identified locations and that this data can be dispersed to subscribers in near real time. This has important implications for dynamic traffic management, road planning and weather and emergency response applications.
Key areas deserving further technical exploration are: development of positioning solutions that address the shortcomings of current GPS-based positioning technologies, such as the inability to receive GPS signals in all situations; development of technical and societal countermeasures to assure the integrity of vehicle safety applications; further refinement of 5.9GHz DSRC communication technology so that it will better support vehicle safety applications; and rolling out the system so that the safety and mobility benefits are sufficient and implemented in a manner that is socially and economically viable.
The US DOT is committed to realising cooperative safety applications using 5.9GHz by fostering research and testing in an open and collaborative partnership with industry, and through this approach to further identify and validate high-value applications, resolve technical issues and identify viable deployment strategies
Editor's note: Although the term 'VII' is now defunct, the results of this work will feed into the IntelliDrive initiative going forward.
